This invention relates to magnetic disk drives and more particularly to an improved exhaust valve for releasing pressurized air from the enclosure of a magnetic disk drive.
Magnetic disk drives are extensively used in digital data processing systems. Examples of high capacity magnetic disk drives include the 8350 disk drive available from Storage Technology Corporation, Louisville, Colo., and the 3350 disk drive available from IBM Corporation, Armonk, N.Y. These disk drives include stacks of rotating magnetic disks with magnetic read/write heads which are positioned over the surfaces of the disks to read and write digital data in magnetic form on the disks. These mechanisms have an extremely high speed of operation. The mechanism tolerances in the positioning of the heads and the disks is critical. Even small particles of dust can cause a malfunction of the machine. Because of this, the head disk assemblies are maintained in a pressurized enclosure. Clean filtered air is continuously supplied to the enclosure to maintain a positive pressure in the enclosure. This prevents the entry of dust and dirt into the enclosure. An exhaust valve is provided for these disk drives. This valve serves the function of releasing pressurized air, maintaining a relatively constant pressure in the enclosure, and closing the exit port when pressure is lost so that no dirt or dust enters through that opening. The prior art exhaust valve in these machines includes a "trap door" which is biased to the closed position but which opens to release pressurized air.
While the prior art air exhaust valves have operated satisfactorily in these disk drives, there is need for improvement, particularly in the reliability of maintaining substantially constant pressure, maintenance required, cost, and positive prevention of back flow of contaminated air into the head disk assembly enclosure.